CVE-2021-46958

MEDIUMNVD 4.74.7

Also known asEUVD-2021-33606 (ENISA EUVD) · GHSA-gmfg-g4f3-5fg9 (GitHub Security Advisories)Source: ENISA EUVD

4.7EG

EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).

Lower severity and no public exploit yet

CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 4.7Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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

btrfs: fix race between transaction aborts and fsyncs leading to use-after-free

There is a race between a task aborting a transaction during a commit, a task doing an fsync and the transaction kthread, which leads to an use-after-free of the log root tree. When this happens, it results in a stack trace like the following:

BTRFS info (device dm-0): forced readonly BTRFS warning (device dm-0): Skipping commit of aborted transaction. BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5) BTRFS warning (device dm-0): Skipping commit of aborted transaction. BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10 BTRFS error (device dm-0): error writing primary super block to device 1 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10 BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers) BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 RIP: 0010:__mutex_lock+0x139/0xa40 Code: c0 74 19 (...) RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202 RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002 RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000 R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040 R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358 FS: 00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? __btrfs_handle_fs_error+0xde/0x146 [btrfs] ? btrfs_sync_log+0x7c1/0xf20 [btrfs] ? btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_file+0x40c/0x580 [btrfs] do_fsync+0x38/0x70 __x64_sys_fsync+0x10/0x20 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fa9142a55c3 Code: 8b 15 09 (...) RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3 RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005 RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340 R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0 Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...) ---[ end trace ee2f1b19327d791d ]---

The steps that lead to this crash are the following:

1) We are at transaction N;

2) We have two tasks with a transaction handle attached to transaction N. Task A and Task B. Task B is doing an fsync;

3) Task B is at btrfs_sync_log(), and has saved fs_info->log_root_tree into a local variable named 'log_root_tree' at the top of btrfs_sync_log(). Task B is about to call write_all_supers(), but before that...

4) Task A calls btrfs_commit_transaction(), and after it sets the transaction state to TRANS_STATE_COMMIT_START, an error happens before it w ---truncated---

CVSS v3: 4.7
EG Score: 4.7MEDIUMmedium confidence
EG Risk: 21
EPSS PROB: 0.2%
EPSS %ILE: 15th
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 (4.7): severity, escalated by confirmed exploitation. This CVE's 4.7 is its impact severity (EG Severity), not escalated.

EG Severity: 4.7 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood: 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). 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 every mission impact level.CISA BOD 26-04: 60 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 every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (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)60 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 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

Published

February 27, 2024

Last Modified

August 5, 2026

References (4)

Affected Packages

(4 across 4 ecosystems)

Debian:11(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.10.38-1: fixed in 5.10.38-1	—

Debian:12(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.10.38-1: fixed in 5.10.38-1	—

Debian:13(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.10.38-1: fixed in 5.10.38-1	—

Debian:14(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.10.38-1: fixed in 5.10.38-1	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-416Use After Free

Data Freshness Timeline

(refreshed 7× in last 7d / 37× 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.

Showing the most recent 97 of 213 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 116 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

2026-11-02 16:38 UTCEPSS rescoreEPSS 0.2% · 15th percentile
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2026-10-25 18:18 UTCEG score recompute
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2026-10-24 21:52 UTCEG score recompute
2026-10-24 21:52 UTCGHSA enrichmentGHSA-gmfg-g4f3-5fg9 · GitHub CVSS 4.7
2026-10-24 16:29 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-10-18 08:50 UTCEG score recompute
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2026-10-13 16:28 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-10-12 19:05 UTCEG score recompute
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2026-10-11 23:31 UTCEG score recompute
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2026-09-30 15:45 UTCEG score recompute
2026-09-30 15:00 UTCEPSS rescoreEPSS 0.2% · 14th percentile
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2026-09-28 13:47 UTCEPSS rescoreEPSS 0.2% · 14th percentile
2026-09-26 20:33 UTCOSV refresh
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2026-08-05 19:15 UTCEPSS rescoreEPSS 0.2% · 15th percentile
2026-08-05 09:46 UTCEG score recompute
2026-08-05 09:46 UTCGHSA enrichmentGHSA-gmfg-g4f3-5fg9 · GitHub CVSS 4.7
2026-08-04 15:06 UTCEPSS rescoreEPSS 0.2% · 15th percentile
2026-08-04 12:22 UTCEG score recompute
2026-08-04 12:22 UTCGHSA enrichmentGHSA-gmfg-g4f3-5fg9 · GitHub CVSS 4.7

Same CWE

10 shown

CWE-416

Frequently asked(5)

What is CVE-2021-46958?

CVE-2021-46958 is a medium-severity vulnerability; its CVE record was published on February 27, 2024. In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race between transaction aborts and fsyncs leading to use-after-free There is a race between a task aborting a transaction during a commit, a task doing an fsync and the transaction kthread, which leads to an…

When was the CVE record for CVE-2021-46958 published?

The CVE record for CVE-2021-46958 was published on February 27, 2024. 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 August 5, 2026; the record at its source may have been updated since.

Is CVE-2021-46958 actively exploited?

CVE-2021-46958 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (15th percentile of EPSS-scored CVEs).

What is the CVSS score of CVE-2021-46958?

CVE-2021-46958 has a CVSS v3 base score of 4.7 (NVD).

How do I remediate CVE-2021-46958?

A fix for CVE-2021-46958 is available: update to the fixed version the vendor names in its advisory.

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CVE-2021-46958

📅 Published

🔄 Last Modified

🔗 References (4)