CVE
One-byte buffer overflow in wide scanf %s and %[ conversions
- Exploited
- No known exploitation
- Fix
- See vendor advisory
- Who is exposed
- Not reported
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 47/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The GNU C Library (glibc) has a one-byte buffer overflow in its wide scanf functions when they handle %s and %[ conversions without the 'l' length modifier. An attacker can trigger it remotely, without logging in, by supplying input whose converted string exactly fills the destination array. The overflow writes an extra null byte just past the end of that array, which may corrupt adjacent data or crash the process.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
Calling the wide scanf family of functions (swscanf, fwscanf, wscanf, vswscanf, vfwscanf and vwscanf) with a %s or %[ conversion without the 'l' length modifier in the GNU C Library version 2.2 to version 2.44 writes an extra null byte one past the end of the destination array when the converted multibyte string and its terminating null byte exactly fill that array.
These conversions store each wide input character into the caller's char array as a multibyte sequence. The conversion ends with the sequence that returns to the initial shift state, which also stores the terminating null byte, and the functions then append a second null byte. A destination sized for the converted string and one terminator, as the C standard requires the caller to provide, is therefore written one byte past its end. The out-of-bounds byte is always a null byte, which may corrupt adjacent data or crash the process. An attacker who supplies the input can trigger the overflow with a string whose converted length exactly fills the destination.
The narrow scanf functions, the %ls and %l[ conversions into a wchar_t array, and the 'a' and 'm' allocation modifiers are not affected, and storing a wide scanf conversion into a narrow char array is uncommon. This issue affects all architectures and ABIs supported by the GNU C Library.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach20/20Affects glibc (software on nearly every server, desktop or phone)
- Severity4.8/10CVSS 4.8
- No patch5/5No fixed version listed; see vendor advisory
What would change the score
- Would score about 92 if added to CISA KEV
- Would score about 87 if CISA's SSVC rates exploitation active
- Would score about 52 if advisories confirm default setups are exposed
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Check whether my systems are affected by CVE-2026-115819 (One-byte buffer overflow in wide scanf %s and %[ conversions), using the cve.now data below.
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What cve.now has for CVE-2026-115819 (entry last updated 2026-11-11):
Affected:
- The GNU C Library glibc: from 2.2, through 2.44
Fixed versions: none listed yet.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-115819 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-115819 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0027
- https://sourceware.org/bugzilla/show_bug.cgi?id=34989
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-115819
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- CVE published
- First seen by cve.now
Affected versions
- The GNU C Library glibc
From 2.2 · through 2.44
Evidence 4
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Write-ups · 1
Establishes: Technical detail and context.
- Report
Other links · 1
- Advisory
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-115819
Is CVE-2026-115819 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-115819?
glibc: from 2.2 through 2.44.Source: cve.now feed data