VulnerabilityPublished 6 May 2026Updated 19 Oct 2026

CVE-2026-43158: Linux kernel · xfs: fix freemap adjustments when adding xattrs to leaf blocks

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 8.8 High · fixed in ef42a8766ff3fdf51cf72fb36d0859c09d134478 : patch Linux kernel soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

8.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS

0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in ef42a8766ff3fdf51cf72fb36d0859c09d134478, d08976725355b9d54d8332fce223fa281cc304a5, a396b3d73d51355e50acdb403ba9c4cae4c1174e +5

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ef42a8766ff3fdf51cf72fb36d0859c09d134478	Fixed in ef42a8766ff3fdf51cf72fb36d0859c09d134478
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < d08976725355b9d54d8332fce223fa281cc304a5	Fixed in d08976725355b9d54d8332fce223fa281cc304a5
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < a396b3d73d51355e50acdb403ba9c4cae4c1174e	Fixed in a396b3d73d51355e50acdb403ba9c4cae4c1174e
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 38613c01f69e1e77e6b8acab1e8ac665d01c2f15	Fixed in 38613c01f69e1e77e6b8acab1e8ac665d01c2f15
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 43f3b18679615a93bd848afde3602ba160637a46	Fixed in 43f3b18679615a93bd848afde3602ba160637a46
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 24ce71852f2cee6581e2cbebc15489ed52bf63b7	Fixed in 24ce71852f2cee6581e2cbebc15489ed52bf63b7

Description

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.

CWE-664Improper Control of a Resource Through its Lifetime (opens in a new tab)
Pillar weakness
The product does not maintain or incorrectly maintains control over a resource throughout its lifetime of creation, use, and release.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Attack patterns
Session Credential Falsification through Forging (opens in a new tab)
Reusing Session IDs (aka Session Replay) (opens in a new tab)
Session Fixation (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
Exploitation of Trusted Identifiers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Affected software

Description

WeaknessesCWE-664

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