CVE-2026-81638 (GCVE-0-2026-81638)
Vulnerability from cvelistv5 – Published: 2026-09-07 22:33 – Updated: 2026-09-08 14:44
VLAI
EPSS
VEX
Title
Non-canonical ULID spellings are accepted and alias to the same record in ash_double_entry
Summary
Improper Handling of Alternate Encoding vulnerability in ash-project ash_double_entry allows an attacker to submit several distinct string spellings of the same identifier.
AshDoubleEntry.ULID renders a 128-bit ULID as 26 Crockford base-32 characters, but the first character encodes only 3 bits, so canonical values are 0 to 7. decode/1 in lib/ulid.ex masks the first character to its low 3 bits and valid?/1 accepts all 32 characters in that position, so 0..., 8..., G... and R... decode to the identical 16-byte value and resolve to the same row. When the type is exposed as a public ID over an HTTP or API boundary, an attacker-supplied ID can be spelled differently from the record it actually reads or writes, desynchronizing or bypassing string-level checks such as idempotency and deduplication keys, deny-lists, audit correlation, or signatures computed over the submitted ID.
This issue affects ash_double_entry: from 0.1.0 before 1.0.19.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-08 14:44 UTC
CWE
- CWE-173 - Improper Handling of Alternate Encoding
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/ash-project/ash_double_entry/s… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-81638.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-81638 | related |
| https://github.com/ash-project/ash_double_entry/c… | patch |
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| ash-project | ash_double_entry |
Affected:
0.1.0 , < 1.0.19
(semver)
cpe:2.3:a:ash-project:ash_double_entry:*:*:*:*:*:*:*:* |
||
| ash-project | ash_double_entry |
Affected:
1e5f7ce8ff25f519c904731a29eb1258324e561a , < d3e688d300a581ae214b3ca7d95ef4de63fbb050
(git)
cpe:2.3:a:ash-project:ash_double_entry:*:*:*:*:*:*:*:* |
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"value": "\u003cp\u003eReachable only when an application exposes \u003ccode\u003eAshDoubleEntry.ULID\u003c/code\u003e as a public identifier over an HTTP or API boundary and performs string-level checks on the submitted ID (idempotency or deduplication keys, deny-lists, audit correlation, or signatures) rather than treating the value as opaque.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Reachable only when an application exposes `AshDoubleEntry.ULID` as a public identifier over an HTTP or API boundary and performs string-level checks on the submitted ID (idempotency or deduplication keys, deny-lists, audit correlation, or signatures) rather than treating the value as opaque."
}
],
"value": "Reachable only when an application exposes AshDoubleEntry.ULID as a public identifier over an HTTP or API boundary and performs string-level checks on the submitted ID (idempotency or deduplication keys, deny-lists, audit correlation, or signatures) rather than treating the value as opaque."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:ash-project:ash_double_entry:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.0.19",
"versionStartIncluding": "0.1.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "reporter",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Zach Daniel / Ash Project"
},
{
"lang": "en",
"type": "coordinator",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eImproper Handling of Alternate Encoding vulnerability in ash-project ash_double_entry allows an attacker to submit several distinct string spellings of the same identifier.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eAshDoubleEntry.ULID\u003c/code\u003e renders a 128-bit ULID as 26 Crockford base-32 characters, but the first character encodes only 3 bits, so canonical values are \u003ccode\u003e0\u003c/code\u003e to \u003ccode\u003e7\u003c/code\u003e. \u003ccode\u003edecode/1\u003c/code\u003e in \u003ccode\u003elib/ulid.ex\u003c/code\u003e masks the first character to its low 3 bits and \u003ccode\u003evalid?/1\u003c/code\u003e accepts all 32 characters in that position, so \u003ccode\u003e0...\u003c/code\u003e, \u003ccode\u003e8...\u003c/code\u003e, \u003ccode\u003eG...\u003c/code\u003e and \u003ccode\u003eR...\u003c/code\u003e decode to the identical 16-byte value and resolve to the same row. When the type is exposed as a public ID over an HTTP or API boundary, an attacker-supplied ID can be spelled differently from the record it actually reads or writes, desynchronizing or bypassing string-level checks such as idempotency and deduplication keys, deny-lists, audit correlation, or signatures computed over the submitted ID.\u003c/p\u003e\n\u003cp\u003eThis issue affects ash_double_entry: from 0.1.0 before 1.0.19.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Improper Handling of Alternate Encoding vulnerability in ash-project ash_double_entry allows an attacker to submit several distinct string spellings of the same identifier.\n\n`AshDoubleEntry.ULID` renders a 128-bit ULID as 26 Crockford base-32 characters, but the first character encodes only 3 bits, so canonical values are `0` to `7`. `decode/1` in `lib/ulid.ex` masks the first character to its low 3 bits and `valid?/1` accepts all 32 characters in that position, so `0...`, `8...`, `G...` and `R...` decode to the identical 16-byte value and resolve to the same row. When the type is exposed as a public ID over an HTTP or API boundary, an attacker-supplied ID can be spelled differently from the record it actually reads or writes, desynchronizing or bypassing string-level checks such as idempotency and deduplication keys, deny-lists, audit correlation, or signatures computed over the submitted ID.\n\nThis issue affects ash_double_entry: from 0.1.0 before 1.0.19."
}
],
"value": "Improper Handling of Alternate Encoding vulnerability in ash-project ash_double_entry allows an attacker to submit several distinct string spellings of the same identifier.\n\nAshDoubleEntry.ULID renders a 128-bit ULID as 26 Crockford base-32 characters, but the first character encodes only 3 bits, so canonical values are 0 to 7. decode/1 in lib/ulid.ex masks the first character to its low 3 bits and valid?/1 accepts all 32 characters in that position, so 0..., 8..., G... and R... decode to the identical 16-byte value and resolve to the same row. When the type is exposed as a public ID over an HTTP or API boundary, an attacker-supplied ID can be spelled differently from the record it actually reads or writes, desynchronizing or bypassing string-level checks such as idempotency and deduplication keys, deny-lists, audit correlation, or signatures computed over the submitted ID.\n\nThis issue affects ash_double_entry: from 0.1.0 before 1.0.19."
}
],
"impacts": [
{
"capecId": "CAPEC-267",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-267 Leverage Alternate Encoding"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 2.1,
"baseSeverity": "LOW",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "LOW",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-173",
"description": "CWE-173 Improper Handling of Alternate Encoding",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-07T22:33:29.297Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/ash-project/ash_double_entry/security/advisories/GHSA-qxp2-vgp9-268q"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-81638.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-81638"
},
{
"tags": [
"patch"
],
"url": "https://github.com/ash-project/ash_double_entry/commit/d3e688d300a581ae214b3ca7d95ef4de63fbb050"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Non-canonical ULID spellings are accepted and alias to the same record in ash_double_entry"
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-81638",
"datePublished": "2026-09-07T22:33:29.297Z",
"dateReserved": "2026-09-07T19:30:01.624Z",
"dateUpdated": "2026-09-08T14:44:19.138Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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