CVE-2025-37879 (GCVE-0-2025-37879)
Vulnerability from cvelistv5 – Published: 2025-05-09 06:45 – Updated: 2026-08-05 11:58
VLAI
EPSS
VEX
Title
9p/net: fix improper handling of bogus negative read/write replies
Summary
In the Linux kernel, the following vulnerability has been resolved:
9p/net: fix improper handling of bogus negative read/write replies
In p9_client_write() and p9_client_read_once(), if the server
incorrectly replies with success but a negative write/read count then we
would consider written (negative) <= rsize (positive) because both
variables were signed.
Make variables unsigned to avoid this problem.
The reproducer linked below now fails with the following error instead
of a null pointer deref:
9pnet: bogus RWRITE count (4294967295 > 3)
Severity
9.8 (Critical)
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
070b3656cf228eaaef7b28b59264c5c7cdbdd0fb , < 468ff4a7c61fb811c596a7c44b6a5455e40fd12b
(git)
Affected: 070b3656cf228eaaef7b28b59264c5c7cdbdd0fb , < a68768e280b7d0c967ea509e791bb9b90adc94a5 (git) Affected: 070b3656cf228eaaef7b28b59264c5c7cdbdd0fb , < c548f95688e2b5ae0e2ae43d53cf717156c7d034 (git) Affected: 070b3656cf228eaaef7b28b59264c5c7cdbdd0fb , < 374e4cd75617c8c2552f562f39dd989583f5c330 (git) Affected: 070b3656cf228eaaef7b28b59264c5c7cdbdd0fb , < d0259a856afca31d699b706ed5e2adf11086c73b (git) |
guessed | |
| Linux | Linux |
Affected:
4.1
Unaffected: 0 , < 4.1 (semver) Unaffected: 6.1.136 , ≤ 6.1.* (semver) Unaffected: 6.6.89 , ≤ 6.6.* (semver) Unaffected: 6.12.26 , ≤ 6.12.* (semver) Unaffected: 6.14.5 , ≤ 6.14.* (semver) Unaffected: 6.15 , ≤ * (original_commit_for_fix) |
guessed |
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"value": "AV:N - The attacker is the remote 9p file server, reachable over the TCP transport (`p9_fd_create_tcp`, port 564) or RDMA; 9p is unauthenticated and unencrypted on the wire, so a malicious server or an on-path MITM can inject the bogus RWRITE reply. The same primitive is available to a malicious hypervisor backend over virtio/Xen.\nAC:L - The server simply answers any TWRITE with a success reply carrying count 0xFFFFFFFF, deterministically bypassing the signed `rsize \u003c written` check. There is no race, no timing window, and no dependence on memory layout to reach the corruption.\nPR:N - The malicious 9p server is a remote peer holding no credentials or account on the victim client; 9p mounts commonly use auth=none, and an on-path attacker needs nothing at all. The mount being present is an environmental precondition, not a privilege held by the attacker.\nUI:N - On an already-mounted 9p share the bug fires on ordinary I/O, including kernel-initiated page-cache writeback via `v9fs_issue_write`, with no victim action required. No specific human interaction beyond the pre-existing mount configuration is needed.\nS:U - The corruption is confined to the 9p client kernel that parsed the reply, with no crossing into a different security authority such as a hypervisor or IOMMU boundary. Impact stays within the victim kernel\u0027s own scope.\nC:H - The over-revert leaves `i-\u003ebvec`/`i-\u003e__iov` pointing before the start of the bio_vec/kvec array, and because `p9_client_write()` keeps looping the next TWRITE marshals data from that out-of-bounds descriptor \u2014 sending adjacent kernel heap or stack memory straight to the attacker-controlled server. This is a repeatable kernel memory disclosure primitive.\nI:H - The same out-of-bounds iterator descriptor supplies attacker-uncontrolled `bv_page`/`iov_base` pointers used for subsequent copies, giving out-of-bounds kernel memory access leveragable for control-flow hijack. Additionally `offset += written` sign-extends the negative count into the u64 file offset and `total` goes negative, corrupting file data placement and netfs transfer accounting.\nA:H - The reported and reproduced result is a NULL pointer dereference in `iov_iter_folioq_revert()` when `folioq-\u003eprev` is NULL at the queue head, and `ITER_UBUF`/`ITER_XARRAY` hit an explicit `BUG()` in `iov_iter_revert()`. The write loop also never terminates because `i-\u003ecount` grows by one each iteration, hanging the task."
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En p9_client_write() y p9_client_read_once(), si el servidor responde incorrectamente con \u00e9xito, pero con un recuento de escrituras/lecturas negativo, se considerar\u00eda que \\\"escrito\\\" (negativo) \u0026lt;= \\\"rsize\\\" (positivo) porque ambas variables estaban firmadas. Para evitar este problema, desactive el signo de las variables. El reproductor enlazado a continuaci\u00f3n ahora falla con el siguiente error en lugar de una referencia de puntero nulo: 9pnet: recuento de RWRITE falso (4294967295 \u0026gt; 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"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-07-30T09:28:00+00:00",
"cve": "CVE-2025-37879",
"id": "CVE-2025-37879",
"initial_release_date": "2025-05-09T00:00:00+00:00",
"product_status:known_affected": "14",
"product_status:known_not_affected": "260",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: 9p/net: fix improper handling of bogus negative read/write replies",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37879.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-08-30T01:58:45Z",
"cve": "CVE-2025-37879",
"id": "CVE-2025-37879",
"initial_release_date": "2025-05-10T02:52:25Z",
"product_status:known_affected": "782",
"product_status:known_not_affected": "6",
"product_status:recommended": "437",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2025-37879",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-37879.json",
"version": "42"
}
}
}
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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.
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.
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