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CVE-2026-120756

Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize

1.9 Low

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
Low

Exploit likelihood

0.18%Unchanged since Nov 4, 2026
90%50%10%1%

What each source reports

CVE List Score used 1.9

Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
CVE-2026-120756
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
Weakness
CWE-125
Updated
2026-11-03
EUVDEUVD-2026-116008 1.9

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
EUVD-2026-116008
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
Updated
2026-11-03
GitHub AdvisoriesGHSA-m9xj-6f2h-rx5r 1.9

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in...

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
GHSA-m9xj-6f2h-rx5r
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
6.1 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Weakness
CWE-125
Updated
2026-11-03
NVD 1.9

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
CVE-2026-120756
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
6.1 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Weakness
CWE-125
Updated
2026-11-04
OSV 1.9

Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
CVE-2026-120756
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
Weakness
CWE-125
Updated
2026-11-05
OSVDEBIAN-CVE-2026-120756 6.1

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
DEBIAN-CVE-2026-120756
CVSS 3.1
6.1 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Updated
2026-11-04
OSVUBUNTU-CVE-2026-120756 1.9

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
UBUNTU-CVE-2026-120756
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CVSS 3.1
6.1 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Updated
2026-11-05
OSVAZL-112634 No score

CVE-2026-120756 affecting package hdf5 1.14.6-6

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Record
AZL-112634
Updated
2026-11-05

Affected products

Affected packages

Affected packages
PackageAffectedFixed
hdf5
Azure Linux:3
through 1.14.6-6 None known
hdf5
Debian:12
All versions, plus listed versions
1.10.10+repack-11.10.10+repack-21.10.10+repack-31.10.10+repack-3.11.10.10+repack-3.2
Show 45 moreShow less
1.10.10+repack-3.2+ports1.10.10+repack-3.31.10.10+repack-41.10.10+repack-51.10.8+repack1-11.12.0+repack-1~exp11.12.0+repack-1~exp21.12.2+repack-1~exp11.14.3+repack-1~exp11.14.3+repack1-1~exp21.14.3+repack1-1~exp31.14.4.3+repack-1~exp11.14.4.3+repack-1~exp21.14.4.3+repack-1~exp31.14.5+repack-11.14.5+repack-1~exp11.14.5+repack-1~exp21.14.5+repack-1~exp31.14.5+repack-1~exp41.14.5+repack-1~exp51.14.5+repack-1~exp61.14.5+repack-21.14.5+repack-31.14.5+repack-3.11.14.5+repack-3~exp11.14.5+repack-3~exp21.14.5+repack-3~exp31.14.5+repack-3~exp41.14.5+repack-41.14.5+repack-4~exp11.14.5+repack-4~exp21.14.5+repack-5~exp21.14.5+repack-5~exp31.14.6+repack-11.14.6+repack-1~exp11.14.6+repack-1~exp101.14.6+repack-1~exp111.14.6+repack-1~exp121.14.6+repack-1~exp131.14.6+repack-1~exp141.14.6+repack-1~exp151.14.6+repack-1~exp161.14.6+repack-1~exp171.14.6+repack-1~exp181.14.6+repack-1~exp19
None known
hdf5
Debian:13
All versions, plus listed versions
1.14.5+repack-31.14.5+repack-3.11.14.5+repack-41.14.5+repack-4~exp11.14.5+repack-4~exp2
Show 42 moreShow less
1.14.5+repack-5~exp21.14.5+repack-5~exp31.14.6+repack-11.14.6+repack-1~exp11.14.6+repack-1~exp101.14.6+repack-1~exp111.14.6+repack-1~exp121.14.6+repack-1~exp131.14.6+repack-1~exp141.14.6+repack-1~exp151.14.6+repack-1~exp161.14.6+repack-1~exp171.14.6+repack-1~exp181.14.6+repack-1~exp191.14.6+repack-1~exp21.14.6+repack-1~exp201.14.6+repack-1~exp211.14.6+repack-1~exp31.14.6+repack-1~exp41.14.6+repack-1~exp51.14.6+repack-1~exp61.14.6+repack-1~exp71.14.6+repack-1~exp81.14.6+repack-1~exp91.14.6+repack-21.14.6+repack-3~exp12.1.0+repack-12.1.0+repack-1~exp102.1.0+repack-1~exp112.1.0+repack-1~exp32.1.0+repack-1~exp42.1.0+repack-1~exp52.1.0+repack-1~exp62.1.0+repack-1~exp72.1.0+repack-1~exp82.1.0+repack-1~exp92.2.0+repack-12.2.0+repack-22.2.0+repack-32.2.0+repack-42.2.0+repack-52.2.0+repack-6
None known
hdf5
Debian:14
All versions, plus listed versions
1.14.5+repack-31.14.5+repack-3.11.14.5+repack-41.14.5+repack-4~exp11.14.5+repack-4~exp2
Show 42 moreShow less
1.14.5+repack-5~exp21.14.5+repack-5~exp31.14.6+repack-11.14.6+repack-1~exp11.14.6+repack-1~exp101.14.6+repack-1~exp111.14.6+repack-1~exp121.14.6+repack-1~exp131.14.6+repack-1~exp141.14.6+repack-1~exp151.14.6+repack-1~exp161.14.6+repack-1~exp171.14.6+repack-1~exp181.14.6+repack-1~exp191.14.6+repack-1~exp21.14.6+repack-1~exp201.14.6+repack-1~exp211.14.6+repack-1~exp31.14.6+repack-1~exp41.14.6+repack-1~exp51.14.6+repack-1~exp61.14.6+repack-1~exp71.14.6+repack-1~exp81.14.6+repack-1~exp91.14.6+repack-21.14.6+repack-3~exp12.1.0+repack-12.1.0+repack-1~exp102.1.0+repack-1~exp112.1.0+repack-1~exp32.1.0+repack-1~exp42.1.0+repack-1~exp52.1.0+repack-1~exp62.1.0+repack-1~exp72.1.0+repack-1~exp82.1.0+repack-1~exp92.2.0+repack-12.2.0+repack-22.2.0+repack-32.2.0+repack-42.2.0+repack-52.2.0+repack-6
None known
hdf5
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
1.8.11-3ubuntu11.8.11-5ubuntu11.8.11-5ubuntu21.8.11-5ubuntu61.8.11-5ubuntu71.8.11-5ubuntu7.11.8.11-5ubuntu7.1+esm11.8.11-5ubuntu7.1+esm2
None known
hdf5
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
1.8.15-patch1+docs-41.8.15-patch1+docs-51.8.16+docs-11.8.16+docs-21.8.16+docs-3
Show 6 moreShow less
1.8.16+docs-3ubuntu11.8.16+docs-41.8.16+docs-4ubuntu11.8.16+docs-4ubuntu1.11.8.16+docs-4ubuntu1.1+esm11.8.16+docs-4ubuntu1.1+esm2
None known
hdf5
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
1.10.0-patch1+docs-41.10.0-patch1+docs-4ubuntu0.1~esm11.10.0-patch1+docs-4ubuntu0.1~esm2
None known
hdf5
Ubuntu:Pro:20.04:LTS
All versions, plus listed versions
1.10.4+repack-101.10.4+repack-111.10.4+repack-11ubuntu11.10.4+repack-11ubuntu1+esm1
None known
hdf5
Ubuntu:22.04:LTS
All versions, plus listed versions
1.10.6+repack-51.10.7+repack-4ubuntu11.10.7+repack-4ubuntu2
None known
hdf5
Ubuntu:24.04:LTS
All versions, plus listed versions
1.10.8+repack1-1ubuntu11.10.10+repack-3ubuntu11.10.10+repack-3.1ubuntu31.10.10+repack-3.1ubuntu4
None known
hdf5
Ubuntu:26.10
All versions, plus listed versions
1.14.6+repack-22.2.0+repack-42.2.0+repack-5
None known
hdf5
Ubuntu:26.04:LTS
All versions, plus listed versions
1.14.5+repack-3build11.14.5+repack-41.14.6+repack-2
None known

History

History
RecordedChangedSources
affected, aliases, referencesOSV
affected, aliases, referencesOSV
referencesOSV
referencesGitHub Advisories, NVD
publishedEUVD
publishedEUVD, NVD
aliases, referencesCVE List, GitHub Advisories, NVD
aliases, products, publishedEUVD
first indexedCVE List

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-120756 is a low vulnerability (CVSS 1.9) in Hdfgroup Hdf5, published November 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. No source names a fixed version.

References

This page doesn't list everything

Left out here: 28 versions. The JSON record has them.

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