diff --git a/src/core/dbus-execute.c b/src/core/dbus-execute.c
index abe009c395..04735354a3 100644
--- a/src/core/dbus-execute.c
+++ b/src/core/dbus-execute.c
@@ -24,7 +24,7 @@
 #include "hexdecoct.h"
 #include "io-util.h"
 #include "ioprio.h"
-#include "journal-util.h"
+#include "journal-file.h"
 #include "mountpoint-util.h"
 #include "namespace.h"
 #include "parse-util.h"
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index ffc58dde9c..4964249bf2 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -38,7 +38,7 @@
 #include "io-util.h"
 #include "ioprio.h"
 #include "ip-protocol-list.h"
-#include "journal-util.h"
+#include "journal-file.h"
 #include "limits-util.h"
 #include "load-fragment.h"
 #include "log.h"
diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index 1d92e15f26..4fae16cea1 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -1521,6 +1521,44 @@ int journal_file_find_data_object(
                         ret, ret_offset);
 }
 
+bool journal_field_valid(const char *p, size_t l, bool allow_protected) {
+        const char *a;
+
+        /* We kinda enforce POSIX syntax recommendations for
+           environment variables here, but make a couple of additional
+           requirements.
+
+           http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html */
+
+        if (l == (size_t) -1)
+                l = strlen(p);
+
+        /* No empty field names */
+        if (l <= 0)
+                return false;
+
+        /* Don't allow names longer than 64 chars */
+        if (l > 64)
+                return false;
+
+        /* Variables starting with an underscore are protected */
+        if (!allow_protected && p[0] == '_')
+                return false;
+
+        /* Don't allow digits as first character */
+        if (p[0] >= '0' && p[0] <= '9')
+                return false;
+
+        /* Only allow A-Z0-9 and '_' */
+        for (a = p; a < p + l; a++)
+                if ((*a < 'A' || *a > 'Z') &&
+                    (*a < '0' || *a > '9') &&
+                    *a != '_')
+                        return false;
+
+        return true;
+}
+
 static int journal_file_append_field(
                 JournalFile *f,
                 const void *field, uint64_t size,
@@ -1534,6 +1572,9 @@ static int journal_file_append_field(
         assert(f);
         assert(field && size > 0);
 
+        if (!journal_field_valid(field, size, true))
+                return -EBADMSG;
+
         hash = journal_file_hash_data(f, field, size);
 
         r = journal_file_find_field_object_with_hash(f, field, size, hash, &o, &p);
diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
index 263d032b90..931c874268 100644
--- a/src/journal/journal-file.h
+++ b/src/journal/journal-file.h
@@ -271,3 +271,5 @@ static inline bool JOURNAL_FILE_COMPRESS(JournalFile *f) {
 }
 
 uint64_t journal_file_hash_data(JournalFile *f, const void *data, size_t sz);
+
+bool journal_field_valid(const char *p, size_t l, bool allow_protected);
diff --git a/src/shared/journal-util.c b/src/shared/journal-util.c
index 29659aa6b7..9e1870e176 100644
--- a/src/shared/journal-util.c
+++ b/src/shared/journal-util.c
@@ -137,41 +137,3 @@ int journal_access_check_and_warn(sd_journal *j, bool quiet, bool want_other_use
 
         return r;
 }
-
-bool journal_field_valid(const char *p, size_t l, bool allow_protected) {
-        const char *a;
-
-        /* We kinda enforce POSIX syntax recommendations for
-           environment variables here, but make a couple of additional
-           requirements.
-
-           http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html */
-
-        if (l == (size_t) -1)
-                l = strlen(p);
-
-        /* No empty field names */
-        if (l <= 0)
-                return false;
-
-        /* Don't allow names longer than 64 chars */
-        if (l > 64)
-                return false;
-
-        /* Variables starting with an underscore are protected */
-        if (!allow_protected && p[0] == '_')
-                return false;
-
-        /* Don't allow digits as first character */
-        if (p[0] >= '0' && p[0] <= '9')
-                return false;
-
-        /* Only allow A-Z0-9 and '_' */
-        for (a = p; a < p + l; a++)
-                if ((*a < 'A' || *a > 'Z') &&
-                    (*a < '0' || *a > '9') &&
-                    *a != '_')
-                        return false;
-
-        return true;
-}
diff --git a/src/shared/journal-util.h b/src/shared/journal-util.h
index db7000ffef..86fcba058d 100644
--- a/src/shared/journal-util.h
+++ b/src/shared/journal-util.h
@@ -6,6 +6,5 @@
 
 #include "sd-journal.h"
 
-bool journal_field_valid(const char *p, size_t l, bool allow_protected);
 int journal_access_blocked(sd_journal *j);
 int journal_access_check_and_warn(sd_journal *j, bool quiet, bool want_other_users);
diff --git a/src/shared/logs-show.c b/src/shared/logs-show.c
index 597ec00ffb..207461034f 100644
--- a/src/shared/logs-show.c
+++ b/src/shared/logs-show.c
@@ -702,9 +702,11 @@ static int output_verbose(
 
                 c = memchr(data, '=', length);
                 if (!c)
-                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                               "Invalid field.");
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid field.");
+
                 fieldlen = c - (const char*) data;
+                if (!journal_field_valid(data, fieldlen, true))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid field.");
 
                 r = field_set_test(output_fields, data, fieldlen);
                 if (r < 0)
@@ -798,6 +800,7 @@ static int output_export(
                 sd_id128_to_string(boot_id, sid));
 
         JOURNAL_FOREACH_DATA_RETVAL(j, data, length, r) {
+                size_t fieldlen;
                 const char *c;
 
                 /* We already printed the boot id from the data in the header, hence let's suppress it here */
@@ -806,10 +809,13 @@ static int output_export(
 
                 c = memchr(data, '=', length);
                 if (!c)
-                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                               "Invalid field.");
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid field.");
 
-                r = field_set_test(output_fields, data, c - (const char *) data);
+                fieldlen = c - (const char*) data;
+                if (!journal_field_valid(data, fieldlen, true))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid field.");
+
+                r = field_set_test(output_fields, data, fieldlen);
                 if (r < 0)
                         return r;
                 if (!r)
@@ -820,11 +826,11 @@ static int output_export(
                 else {
                         uint64_t le64;
 
-                        fwrite(data, c - (const char*) data, 1, f);
+                        fwrite(data, fieldlen, 1, f);
                         fputc('\n', f);
-                        le64 = htole64(length - (c - (const char*) data) - 1);
+                        le64 = htole64(length - fieldlen - 1);
                         fwrite(&le64, sizeof(le64), 1, f);
-                        fwrite(c + 1, length - (c - (const char*) data) - 1, 1, f);
+                        fwrite(c + 1, length - fieldlen - 1, 1, f);
                 }
 
                 fputc('\n', f);
@@ -961,6 +967,7 @@ static int update_json_data_split(
                 const void *data,
                 size_t size) {
 
+        size_t fieldlen;
         const char *eq;
         char *name;
 
@@ -974,14 +981,15 @@ static int update_json_data_split(
         if (!eq)
                 return 0;
 
-        if (eq == data)
-                return 0;
+        fieldlen = eq - (const char*) data;
+        if (!journal_field_valid(data, fieldlen, true))
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid field.");
 
-        name = strndupa(data, eq - (const char*) data);
+        name = strndupa(data, fieldlen);
         if (output_fields && !set_contains(output_fields, name))
                 return 0;
 
-        return update_json_data(h, flags, name, eq + 1, size - (eq - (const char*) data) - 1);
+        return update_json_data(h, flags, name, eq + 1, size - fieldlen - 1);
 }
 
 static int output_json(
diff --git a/src/systemctl/systemctl-show.c b/src/systemctl/systemctl-show.c
index fabaa545e1..d5efecbe65 100644
--- a/src/systemctl/systemctl-show.c
+++ b/src/systemctl/systemctl-show.c
@@ -16,7 +16,7 @@
 #include "hexdecoct.h"
 #include "hostname-util.h"
 #include "in-addr-util.h"
-#include "journal-util.h"
+#include "journal-file.h"
 #include "list.h"
 #include "locale-util.h"
 #include "memory-util.h"
diff --git a/test/fuzz/fuzz-journal-remote/oss-fuzz-25353 b/test/fuzz/fuzz-journal-remote/oss-fuzz-25353
new file mode 100644
index 0000000000..94e5fbb93e
Binary files /dev/null and b/test/fuzz/fuzz-journal-remote/oss-fuzz-25353 differ