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CVE-2026-8257

WebAssembly Binaryen BrOn wasm-ir-builder.cpp makeBrOn assertion

4.8 MediumFix available

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.16%Up 0.1 points since May 11, 2026
90%50%10%1%

What each source reports

CVE List Score used 4.8

WebAssembly Binaryen BrOn wasm-ir-builder.cpp makeBrOn assertion

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
CVE-2026-8257
CVSS 4.0
4.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CVSS 3.1
3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CVSS 3.0
3.3 LowCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CVSS 2.0
1.7 AV:L/AC:L/Au:S/C:N/I:N/A:P/E:POC/RL:OF/RC:C
Weakness
CWE-617
Updated
2026-11-02
EUVDEUVD-2026-29013 4.8

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
EUVD-2026-29013
CVSS 4.0
4.8 MediumCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
Updated
2026-11-02
GitHub AdvisoriesGHSA-gmmj-chcc-2f2x 1.9

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function...

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
GHSA-gmmj-chcc-2f2x
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/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
3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-617
Updated
2026-11-02
NVD 1.9

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
CVE-2026-8257
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/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
3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
1.7 LowAV:L/AC:L/Au:S/C:N/I:N/A:P
Weakness
CWE-617
Updated
2026-11-02
OSV 1.9

WebAssembly Binaryen BrOn wasm-ir-builder.cpp makeBrOn assertion

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
CVE-2026-8257
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
Weakness
CWE-617
Updated
2026-11-02
OSVDEBIAN-CVE-2026-8257 5.5

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
DEBIAN-CVE-2026-8257
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-03
OSVJLSEC-2026-1094 1.9

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function...

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
JLSEC-2026-1094
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/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 2.0
1.7 LowAV:L/AC:L/Au:S/C:N/I:N/A:P
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-8257 1.9

A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.

Record
UBUNTU-CVE-2026-8257
CVSS 4.0
1.9 LowCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CVSS 3.1
5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1
3.3 LowCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-02
OSVopenSUSE-SU-2026:11915-1 No score

binaryen-133-1.1 on GA media

These are all security issues fixed in the binaryen-133-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11915-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
binaryen
Debian:12
 All versions, plus listed versions
108-1112-1116-1120-1120-2
Show 11 moreShow less
120-3120-4120-4+ports122-1.1122-2122-3130-1130-2130-3131-1131-2
 None known
binaryen
Debian:13
 All versions, plus listed versions
120-4120-4+ports122-1.1122-2122-3
Show 5 moreShow less
130-1130-2130-3131-1131-2
 None known
binaryen
Debian:14
 before 130-2, plus listed versions
120-4120-4+ports122-1.1122-2122-3130-1
130-2
Binaryen_jll
Julia
 before 0.130.0+0
0.130.0+0
binaryen
Ubuntu:20.04:LTS
 All versions, plus listed versions
89-190-191-1
 None known
binaryen
Ubuntu:22.04:LTS
 All versions, plus listed versions
99-3105-1
 None known
binaryen
Ubuntu:24.04:LTS
 All versions, plus listed versions
108-1
 None known
binaryen
Ubuntu:25.10
 All versions, plus listed versions
120-3120-4
 None known
binaryen
Ubuntu:26.10
 All versions, plus listed versions
120-4build1130-2130-3131-2
 None known
binaryen
Ubuntu:26.04:LTS
 All versions, plus listed versions
120-4120-4build1
 None known
binaryen
openSUSE:Tumbleweed
From an advisory covering 3 CVEs
 before 133-1.1
133-1.1

History

History
RecordedChangedSources
affected
affected, factsOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

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

In short

CVE-2026-8257 is a medium vulnerability (CVSS 4.8) in Webassembly Binaryen, published May 11, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 5th percentile. Fixed in binaryen 130-2.

References

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