In the Linux kernel, the following vulnerability has been resolved:
ext4: avoid infinite loops caused by residual data
On the mkdir/mknod path, when mapping logical blocks to physical blocks,
if inserting a new extent into the extent tree fails (in this example,
because the file system disabled the huge file feature when marking the
inode as dirty), ext4_ext_map_blocks() only calls ext4_free_blocks() to
reclaim the physical block without deleting the corresponding data in
the extent tree. This causes subsequent mkdir operations to reference
the previously reclaimed physical block number again, even though this
physical block is already being used by the xattr block. Therefore, a
situation arises where both the directory and xattr are using the same
buffer head block in memory simultaneously.
The above causes ext4_xattr_block_set() to enter an infinite loop about
"inserted" and cannot release the inode lock, ultimately leading to the
143s blocking problem mentioned in [1].
If the metadata is corrupted, then trying to remove some extent space
can do even more harm. Also in case EXT4_GET_BLOCKS_DELALLOC_RESERVE
was passed, remove space wrongly update quota information.
Jan Kara suggests distinguishing between two cases:
1) The error is ENOSPC or EDQUOT - in this case the filesystem is fully
consistent and we must maintain its consistency including all the
accounting. However these errors can happen only early before we've
inserted the extent into the extent tree. So current code works correctly
for this case.
2) Some other error - this means metadata is corrupted. We should strive to
do as few modifications as possible to limit damage. So I'd just skip
freeing of allocated blocks.
[1]
INFO: task syz.0.17:5995 blocked for more than 143 seconds.
Call Trace:
inode_lock_nested include/linux/fs.h:1073 [inline]
__start_dirop fs/namei.c:2923 [inline]
start_dirop fs/namei.c:2934 [inline]
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.4): severity, escalated by confirmed exploitation. This CVE's 9.4 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.4 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it