CVE-2026-98959

CRITICALPre-NVD 9.89.8
EchelonGraph scoreHIGH confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-10-23. A secondary CVSS source baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this week

Also known asEUVD-2026-108753 (ENISA EUVD) · GHSA-cf5f-cwf6-82gc (GitHub Security Advisories)Source: ENISA EUVD

9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix xattr replace when multiple xattrs are packed in the same item

If we have a btrfs_dir_item item that packs multiple xattrs and then we replace the value of one of them (with the setxattr(2) family of syscalls) with another value of a different size, we end up not having a fully initialized btrfs_dir_item, resulting in a corruption that the tree checker will detect at extent buffer writeback time.

This is because in btrfs_setxattr() when we find a btrfs_dir_item with multiple xattrs (due to the crc32c hash of their name being the same) we delete one of the xattr items (btrfs_dir_item) and then insert a new one, but the deletion and insertion results in shifting existing data in the leaf and therefore when the new value of a xattr has a different size, the new btrfs_dir_item is placed in a leaf section that was not initialized and we only copy the value's data and set the value's length in the new btrfs_dir_item, without setting the name, the name's length, the key (which must be all zeroes for xattrs), flags (BTRFS_FT_XATTR) and transaction ID.

The following script reproduces the issue:

$ cat test.sh #!/bin/bash

DEV=/dev/sdi MNT=/mnt/sdi

mkfs.btrfs -f $DEV mount $DEV $MNT

touch $MNT/testfile

# Add two xattrs that, on btrfs, have the same hash (crc32c) for their # name and therefore are packed into the same btrfs_dir_item. setfattr -n user.foobar -v 123 $MNT/testfile setfattr -n user.WvG1c1Td -v qwerty $MNT/testfile

# Verify the xattrs are present. echo "xattrs before:" getfattr --absolute-names --dump $MNT/testfile

# Now replace the value of the foobar xattr with a significantly larger # value. setfattr -n user.foobar -v abcdefghijklmnopqrstuvwxyz $MNT/testfile

# Check the xattrs have the expected values. echo "xattrs after:" getfattr --absolute-names --dump $MNT/testfile

umount $MNT

Running it:

$ ./test.sh (...) xattrs before: # file: /mnt/sdi/testfile user.WvG1c1Td="qwerty" user.foobar="123"

xattrs after: # file: /mnt/sdi/testfile user.WvG1c1Td="qwerty"

So the "user.foobar" xattr is missing and there was a transaction abort when unmounting the fs with the following traces in dmesg:

$ dmesg [869800.159271] BTRFS warning (device sdi): access to eb bytenr 30474240 len 16384 out of range start 16015 len 25964 [869800.159293] ------------[ cut here ]------------ [869800.159296] WARNING: fs/btrfs/extent_io.c:4408 at report_eb_range+0x44/0x60 [btrfs], CPU#8: getfattr/2605179 [869800.168961] Modules linked in: btrfs dm_thin_pool (...) [869800.190527] CPU: 8 UID: 0 PID: 2605179 Comm: getfattr Tainted: G W 7.3.0-rc3-btrfs-next-244+ #1 PREEMPT(full) [869800.193726] Tainted: [W]=WARN [869800.194502] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [869800.197576] RIP: 0010:report_eb_range+0x44/0x60 [btrfs] [869800.198985] Code: 48 8b 7b 18 (...) [869800.203531] RSP: 0018:ffffce4541937d58 EFLAGS: 00010246 [869800.204609] RAX: 0000000000000000 RBX: ffff8dde054b8738 RCX: 0000000000000000 [869800.206137] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffc04c92a0 [869800.207645] RBP: 0000000000003e8f R08: 0000000000000000 R09: 3fffffffffefffff [869800.226175] R10: ffffce4541937a88 R11: 0000000000000003 R12: 000000000000656c [869800.227594] R13: ffff8dde14be800f R14: 000000000000656c R15: 0000000000000069 [869800.229097] FS: 00007f59023bb780(0000) GS:ffff8de5788ed000(0000) knlGS:0000000000000000 [869800.231137] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [869800.232321] CR2: 0000558dc45e6a78 CR3: 0000000765b16004 CR4: 0000000000370ef0 [869800.233783] Call Trace: [869800.234330] [869800.234791] read_extent_buffer+0x4d/0x100 [btrfs] [869800.235898] btrfs_listxattr+0x199/0x240 [btrfs] [869800.236912] vfs_listxattr+0x51/0 ---truncated---

CVSS v3
9.8
EG Score
9.8CRITICALhigh confidence
EG Risk
44
EG Risk 44/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.6% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.6%
EPSS %ILE
49th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-02). 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, and whom BOD 26-04 binds: 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 (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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

Published

October 23, 2026

Last Modified

October 24, 2026

Advisory Details (5)

Auto-updated Oct 31, 2026
Patch available.
Web page

btrfs: fix xattr replace when multiple xattrs are packed in the same item - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/c1803697a60f22743aa28ad522f805e92d45e3f0
Web page

btrfs: fix xattr replace when multiple xattrs are packed in the same item - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/a97114b9b00ed3d05156f3b2ddbf797296260389
Web page

btrfs: fix xattr replace when multiple xattrs are packed in the same item - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/858bee1c77857aabcc2327cd32dd8266332de332
Web page

btrfs: fix xattr replace when multiple xattrs are packed in the same item - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7a53bb4668b319fc6c8a3ce2c21635125c7d2712
Web page

btrfs: fix xattr replace when multiple xattrs are packed in the same item - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5877d7138cc4359d26fd7b010eedfd1b3162348f

Vendor Advisories for CVE-2026-98959(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Data Freshness Timeline

(refreshed 24× in last 7d / 44× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-11-03 16:49 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  2. 2026-11-03 00:55 UTCEG score recompute
  3. 2026-11-03 00:55 UTCVendor advisory
  4. 2026-11-03 00:55 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  5. 2026-11-02 16:46 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  6. 2026-11-01 23:48 UTCEG score recompute
  7. 2026-11-01 23:48 UTCVendor advisory
  8. 2026-11-01 23:48 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  9. 2026-11-01 16:36 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  10. 2026-10-31 22:40 UTCEG score recompute
  11. 2026-10-31 22:40 UTCVendor advisory
  12. 2026-10-31 22:40 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  13. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.6% · 49th percentile
  14. 2026-10-30 21:33 UTCEG score recompute
  15. 2026-10-30 21:33 UTCVendor advisory
  16. 2026-10-30 21:33 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  17. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  18. 2026-10-29 20:26 UTCEG score recompute
  19. 2026-10-29 20:26 UTCVendor advisory
  20. 2026-10-29 20:26 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  21. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  22. 2026-10-28 19:18 UTCEG score recompute
  23. 2026-10-28 19:18 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  24. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  25. 2026-10-27 18:11 UTCEG score recompute
Show 19 more
  1. 2026-10-27 18:11 UTCVendor advisory
  2. 2026-10-27 18:11 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-27 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  4. 2026-10-26 17:04 UTCEG score recompute
  5. 2026-10-26 17:04 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-26 16:33 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  7. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.6% · 48th percentile
  8. 2026-10-25 15:39 UTCEG score recompute
  9. 2026-10-25 15:39 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc · GitHub severity CRITICAL · GitHub CVSS 9.8
  10. 2026-10-25 13:46 UTCEG score recompute
  11. 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  12. 2026-10-24 14:26 UTCEG score recompute
  13. 2026-10-24 14:26 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc
  14. 2026-10-24 14:14 UTCEG score recomputeFirst assessed: 9.8 CRITICAL
  15. 2026-10-24 14:14 UTCGHSA enrichmentGHSA-cf5f-cwf6-82gc
  16. 2026-10-24 14:13 UTCMITRE cvelistV5CVSS v3 → 9.8 · severity → CRITICAL
  17. 2026-10-23 13:25 UTCNVD update
  18. 2026-10-23 12:25 UTCEG score recompute
  19. 2026-10-23 12:24 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-98959?
CVE-2026-98959 is a critical-severity vulnerability; its CVE record was published on October 23, 2026. In the Linux kernel, the following vulnerability has been resolved: btrfs: fix xattr replace when multiple xattrs are packed in the same item If we have a btrfs_dir_item item that packs multiple xattrs and then we replace the value of one of them (with the setxattr(2) family of syscalls) with…
When was the CVE record for CVE-2026-98959 published?
The CVE record for CVE-2026-98959 was published on October 23, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 24, 2026; the record at its source may have been updated since.
Is CVE-2026-98959 actively exploited?
CVE-2026-98959 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (49th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-98959?
CVE-2026-98959 has a CVSS base score of 9.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-98959?
A fix for CVE-2026-98959 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-98959 are linked in the Vendor Advisories panel on this page.

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