NULL Pointer Dereference in H5HL_unprotect via Corrupted File
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 2.3.0
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.3.0.
- Exploitation0/40No signal
- Exposure?/25Exposure: unknown (data gap). No advisory context yet
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity5.4/10CVSS 5.4
- No patch0/5No signal
What would change the score
- Would score about 60 if added to CISA KEV
- Would score about 55 if CISA's SSVC rates exploitation active
- Would score about 27 if advisories confirm default setups are exposed
CVE-2026-120758 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.4 (medium) and affects HDF5; fixed in 2.3.0.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- 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? →
- 5/100 · provisional
- Fix
- Fixed in 2.3.0
- 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
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
HDF5, through version 2.2.0 is not allowed, so: The HDF5 library (its local heap handling, in the H5HL_unprotect function) is affected, and a specially crafted HDF5 file can cause it to crash via a NULL pointer dereference, resulting in denial of service for applications that open and traverse the malicious file.
Read the original description
HDF5 through 2.2.0 contains a NULL pointer dereference vulnerability in H5HL_unprotect() in src/H5HL.c. H5HL_protect() pins a single metadata cache entry for a local heap, either the heap prefix or the separate data block, and H5HL_unprotect() unpins it on the final unprotect. When the metadata cache destroys a corrupted local heap entry, H5HL__prfx_dest() unlinks it from the heap by setting heap->prfx or heap->dblk to NULL. A crafted HDF5 file can therefore reach H5HL_unprotect() with no cached object to unpin, and the function passes the NULL pointer to H5AC_unpin_entry(). This causes an assertion failure in debug builds and a NULL pointer dereference and crash in release builds. An attacker who can get a user or application to open and traverse a malicious file can cause a denial of service.
What to do
Upgrade to a fixed version: 2.3.0.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- The HDF Group HDF5
fixed in 2.3.0
Evidence 1
- Repository
Corrections
None so far.
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Questions about CVE-2026-120758
Is CVE-2026-120758 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-2026-120758?
HDF5: before 2.3.0.Source: cve.now feed data
How do I fix CVE-2026-120758?
Upgrade to a fixed version: 2.3.0.Source: cve.now feed data