Heap-based buffer overflow in the string_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code
Heap-based buffer overflow in the string_vformat function in string.c in Exim before 4.70 allows remote attackers to execute arbitrary code via an SMTP session that includes two MAIL commands in conjunction with a large message containing crafted headers, leading to improper rejection logging.
- Published
- Dec 14, 2010
- Updated
- Jun 16, 2026
- EPSS
- 71.7% · 99th percentile
- CWE
- CWE-787
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Report tools
Action score
91
Now
Patch today or shut off access.
- CVSS
- 39 / 40 · 9.8 / 10
- CISA KEV
- 30 / 30 · Listed
- EPSS
- 22 / 30 · 71.7%
CISA SSVC decision
- Exploitation
- active
- Automatable
- yes
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
Actively exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on Mar 25, 2022. That signals real attacks, not theory.
Remediation deadline for government agencies: Apr 15, 2022.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| exim | exim | cpe:2.3:a:exim:exim |
| opensuse | opensuse | cpe:2.3:o:opensuse:opensuse |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| canonical | ubuntu linux | cpe:2.3:o:canonical:ubuntu_linux |
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Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- exim eximbefore 4.70
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | exim4 | before 4.70-1 | 4.70-1 |
| Debian:5.0 | exim4 | before 4.69-9+lenny1 | 4.69-9+lenny1 |
| openSUSE:Tumbleweed | exim | before 4.86.2-2.2 | 4.86.2-2.2 |
| Red Hat:enterprise_linux:4::as | exim | before 0:4.43-1.RHEL4.5.el4_8.1 | 0:4.43-1.RHEL4.5.el4_8.1 |
| Red Hat:enterprise_linux:4::as | exim-debuginfo | before 0:4.43-1.RHEL4.5.el4_8.1 | 0:4.43-1.RHEL4.5.el4_8.1 |
| Red Hat:enterprise_linux:4::as | exim-doc | before 0:4.43-1.RHEL4.5.el4_8.1 | 0:4.43-1.RHEL4.5.el4_8.1 |
| Red Hat:enterprise_linux:4::as | exim-mon | before 0:4.43-1.RHEL4.5.el4_8.1 | 0:4.43-1.RHEL4.5.el4_8.1 |
| Red Hat:enterprise_linux:4::as | exim-sa | before 0:4.43-1.RHEL4.5.el4_8.1 | 0:4.43-1.RHEL4.5.el4_8.1 |
| Red Hat:enterprise_linux:5::client | exim | before 0:4.63-5.el5_5.2 | 0:4.63-5.el5_5.2 |
| Red Hat:enterprise_linux:5::client | exim-debuginfo | before 0:4.63-5.el5_5.2 | 0:4.63-5.el5_5.2 |
| Red Hat:enterprise_linux:5::client | exim-mon | before 0:4.63-5.el5_5.2 | 0:4.63-5.el5_5.2 |
| Red Hat:enterprise_linux:5::client | exim-sa | before 0:4.63-5.el5_5.2 | 0:4.63-5.el5_5.2 |
| Red Hat:rhel_eus:4.7::as | exim | before 0:4.43-1.RHEL4.5.el4_7.1 | 0:4.43-1.RHEL4.5.el4_7.1 |
| Red Hat:rhel_eus:4.7::as | exim-debuginfo | before 0:4.43-1.RHEL4.5.el4_7.1 | 0:4.43-1.RHEL4.5.el4_7.1 |
| Red Hat:rhel_eus:4.7::as | exim-doc | before 0:4.43-1.RHEL4.5.el4_7.1 | 0:4.43-1.RHEL4.5.el4_7.1 |
| Red Hat:rhel_eus:4.7::as | exim-mon | before 0:4.43-1.RHEL4.5.el4_7.1 | 0:4.43-1.RHEL4.5.el4_7.1 |
| Red Hat:rhel_eus:4.7::as | exim-sa | before 0:4.43-1.RHEL4.5.el4_7.1 | 0:4.43-1.RHEL4.5.el4_7.1 |
| Red Hat:rhel_eus:5.3 | exim | before 0:4.63-3.el5_3.1 | 0:4.63-3.el5_3.1 |
| Red Hat:rhel_eus:5.3 | exim-debuginfo | before 0:4.63-3.el5_3.1 | 0:4.63-3.el5_3.1 |
| Red Hat:rhel_eus:5.3 | exim-mon | before 0:4.63-3.el5_3.1 | 0:4.63-3.el5_3.1 |
| Red Hat:rhel_eus:5.3 | exim-sa | before 0:4.63-3.el5_3.1 | 0:4.63-3.el5_3.1 |
| Red Hat:rhel_eus:5.4 | exim | before 0:4.63-3.el5_4.1 | 0:4.63-3.el5_4.1 |
| Red Hat:rhel_eus:5.4 | exim-debuginfo | before 0:4.63-3.el5_4.1 | 0:4.63-3.el5_4.1 |
| Red Hat:rhel_eus:5.4 | exim-mon | before 0:4.63-3.el5_4.1 | 0:4.63-3.el5_4.1 |
+1
Same product
exim: all recordsOther highest-scoring records for the same primary product.
- CVE-2019-10149A flaw was found in Exim versions 4.87 to 4.91 (inclusive).KEV99Now
- CVE-2018-6789An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1.KEV94Now
- CVE-2019-16928Exim 4.92 through 4.92.2 allows remote code execution, a different vulnerability than CVE-2019-15846.KEV81Now
- CVE-2010-4345Exim 4.72 and earlier allows local users to gain privileges by leveraging the ability of the exim user account to specify an alternate confiKEV66This week
- CVE-2025-26794Exim 4.98 before 4.98.1, when SQLite hints and ETRN serialization are used, allows remote SQL injection.62This week
- CVE-2020-28018Exim 4 before 4.94.2 allows Use After Free in smtp_reset in certain situations that may be common for builds with OpenSSL.56Plan
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Debian:exim4 | 4.70-1 · Debian:12 | Package registry (OSV) |
| openSUSE:exim | 4.86.2-2.2 · openSUSE:Tumbleweed | Package registry (OSV) |
| Red Hat:exim | 0:4.43-1.RHEL4.5.el4_7.1 · Red Hat:rhel_eus:4.7::as | Package registry (OSV) |
| Red Hat:exim-debuginfo | 0:4.43-1.RHEL4.5.el4_7.1 · Red Hat:rhel_eus:4.7::as | Package registry (OSV) |
| Red Hat:exim-doc | 0:4.43-1.RHEL4.5.el4_7.1 · Red Hat:rhel_eus:4.7::as | Package registry (OSV) |
| Red Hat:exim-mon | 0:4.43-1.RHEL4.5.el4_7.1 · Red Hat:rhel_eus:4.7::as | Package registry (OSV) |
| Red Hat:exim-sa | 0:4.43-1.RHEL4.5.el4_7.1 · Red Hat:rhel_eus:4.7::as | Package registry (OSV) |
Exploit status
Weaponized
A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.
Evidence
- Metasploit module ×1
- Exploit-DB entry ×2
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Exploit-DB entry | remote | 2010-12-11 |
| Exploit-DB entry | remote | 2010-12-16 |
| Metasploit module | exploit/unix/smtp/exim4_string_formatExim4 string_format Function Heap Buffer Overflowexploit | 2010-12-07 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Metasploit-8 d
- First PoC-4 d
- Published
- CISA KEV+4118 d
- TodaySep 29, 2026+5768 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- ftp://ftp.exim.org/pub/exim/ChangeLogs/ChangeLog-4.70
- atmail.com/blog/2010/atmail-6204-now-available/
- bugs.exim.org/show_bug.cgi?id=787
- git.exim.org/exim.git/commit/24c929a27415c7cfc7126c47e4cad39acf3efa6b
- lists.exim.org/lurker/message/20101210.164935.385e04d0.en.html
- lists.opensuse.org/opensuse-security-announce/2010-12/msg00003.html
- openwall.com/lists/oss-security/2010/12/10/1
- secunia.com/advisories/40019
- secunia.com/advisories/42576
- secunia.com/advisories/42586
- secunia.com/advisories/42587
- secunia.com/advisories/42589
- www.cpanel.net/2010/12/exim-remote-memory-corruption-vulnerability-notification-cve-2010-4344.html
- www.debian.org/security/2010/dsa-2131
- www.kb.cert.org/vuls/id/682457
- www.metasploit.com/modules/exploit/unix/smtp/exim4_string_format
- www.redhat.com/support/errata/RHSA-2010-0970.html
- www.securityfocus.com/archive/1/515172/100/0/threaded
- www.securityfocus.com/bid/45308
- www.securitytracker.com/id?1024858
Vendor advisories and official records. Exploit/PoC links are deliberately left out.