CVE-2021-47107
In the Linux kernel, the following vulnerability has been resolved: NFSD: Fix READDIR buffer overflow If a client sends a READDIR count argument that is too small (say, zero), then the buffer size calculation in the new init_dirlist helper functions…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.85%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: NFSD: Fix READDIR buffer overflow If a client sends a READDIR count argument that is too small (say, zero), then the buffer size calculation in the new init_dirlist helper functions results in an underflow, allowing the XDR stream functions to write beyond the actual buffer. This calculation has always been suspect. NFSD has never sanity- checked the READDIR count argument, but the old entry encoders managed the problem correctly. With the commits below, entry encoding changed, exposing the underflow to the pointer arithmetic in xdr_reserve_space(). Modern NFS clients attempt to retrieve as much data as possible for each READDIR request. Also, we have no unit tests that exercise the behavior of READDIR at the lower bound of @count values. Thus this case was missed during testing.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.85% probability · 56th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-120
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/53b1119a6e5028b125f431a0116ba73510d82a72Exploit, Mailing List, Patch
- https://git.kernel.org/stable/c/9e291a6a28d32545ed2fd959a8165144d1724df1Exploit, Mailing List, Patch
- https://git.kernel.org/stable/c/eabc0aab98e5218ceecd82069b0d6fdfff5ee885Exploit, Mailing List, Patch
- https://git.kernel.org/stable/c/53b1119a6e5028b125f431a0116ba73510d82a72Exploit, Mailing List, Patch
- https://git.kernel.org/stable/c/9e291a6a28d32545ed2fd959a8165144d1724df1Exploit, Mailing List, Patch
- https://git.kernel.org/stable/c/eabc0aab98e5218ceecd82069b0d6fdfff5ee885Exploit, Mailing List, Patch
- https://cert-portal.siemens.com/productcert/html/ssa-265688.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.