Out-of-Bounds Write in Linux kernel (CVE-2021-47366)
Summary
Out-of-bounds write in Linux kernel (CVE-2021-47366). Data can be tampered with by attackers.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix corruption in reads at fpos 2G-4G from an OpenAFS server
AFS-3 has two data fetch RPC variants, FS.FetchData and FS.FetchData64, and
Linux's afs client switches between them when talking to a non-YFS server
if the read size, the file position or the sum of the two have the upper 32
bits set of the 64-bit value.
This is a problem, however, since the file position and length fields of
FS.FetchData are signed 32-bit values.
Fix this by capturing the capability bits obtained from the fileserver when
it's sent an FS.GetCapabilities RPC, rather than just discarding them, and
then picking out the VICED_CAPABILITY_64BITFILES flag. This can then be
used to decide whether to use FS.FetchData or FS.FetchData64 - and also
FS.StoreData or FS.StoreData64 - rather than using upper_32_bits() to
switch on the parameter values.
This capabilities flag could also be used to limit the maximum size of the
file, but all servers must be checked for that.
Note that the issue does not exist with FS.StoreData - that uses unsigned
32-bit values. It's also not a problem with Auristor servers as its
YFS.FetchData64 op uses unsigned 64-bit values.
This can be tested by cloning a git repo through an OpenAFS client to an
OpenAFS server and then doing "git status" on it from a Linux afs
client[1]. Provided the clone has a pack file that's in the 2G-4G range,
the git status will show errors like:
error: packfile .git/o…
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-47366 has been found in Linux kernel.
Data can be tampered with by attackers. CVSS score: 7.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2021-47366" on the vendor's site.
CVE-2021-47366 (Linux kernel) — CWE-787 / CVSS v3 7.1
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Out-of-bounds write (CWE-787) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.1/10). Data can be tampered with by attackers.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2021-47366 linux Fixed in: 5.14.9-1
- Ubuntu UBUNTU-CVE-2021-47366 linux
References
- patch git.kernel.org
- patch git.kernel.org