In the Linux kernel, the following vulnerability has been resolved:
xfs: fix freemap adjustments when adding xattrs to leaf blocks
xfs/592 and xfs/794 both trip this assertion in the leaf block freemap
adjustment code after ~20 minutes of running on my test VMs:
ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t)
+ xfs_attr3_leaf_hdr_size(leaf));
Upon enabling quite a lot more debugging code, I narrowed this down to
fsstress trying to set a local extended attribute with namelen=3 and
valuelen=71. This results in an entry size of 80 bytes.
At the start of xfs_attr3_leaf_add_work, the freemap looks like this:
i 0 base 448 size 0 rhs 448 count 46
i 1 base 388 size 132 rhs 448 count 46
i 2 base 2120 size 4 rhs 448 count 46
firstused = 520
where "rhs" is the first byte past the end of the leaf entry array.
This is inconsistent -- the entries array ends at byte 448, but
freemap[1] says there's free space starting at byte 388!
By the end of the function, the freemap is in worse shape:
i 0 base 456 size 0 rhs 456 count 47
i 1 base 388 size 52 rhs 456 count 47
i 2 base 2120 size 4 rhs 456 count 47
firstused = 440
Important note: 388 is not aligned with the entries array element size
of 8 bytes.
Based on the incorrect freemap, the name area starts at byte 440, which
is below the end of the entries array! That's why the assertion
triggers and the filesystem shuts down.
How did we end up here? First, recall from the previous patch that the
freemap array in an xattr leaf block is not intended to be a
comprehensive map of all free space in the leaf block. In other words,
it's perfectly legal to have a leaf block with:
* 376 bytes in use by the entries array
* freemap[0] has [base = 376, size = 8]
* freemap[1] has [base = 388, size = 1500]
* the space between 376 and 388 is free, but the freemap stopped
tracking that some time ago
If we add one xattr, the entries array grows to 384 bytes, and
freemap[0] becomes [base = 384, size = 0]. So far, so good. But if we
add a second xattr, the entries array grows to 392 bytes, and freemap[0]
gets pushed up to [base = 392, size = 0]. This is bad, because
freemap[1] hasn't been updated, and now the entries array and the free
space claim the same space.
The fix here is to adjust all freemap entries so that none of them
collide with the entries array. Note that this fix relies on commit
2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow") and
the previous patch that resets zero length freemap entries to have
base = 0.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (8.8): severity, escalated by confirmed exploitation. This CVE's 8.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.8 HIGHCVSS-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 2026-10-27). 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; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade 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; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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